Parking assistance device, parking assistance method, and non-transitory computer readable medium

ABSTRACT

A parking assistance device includes an imager that captures an image of a surrounding of a vehicle, and a display that displays a guidance image for guiding the vehicle from a parking start position to a target parking position and displays a moving area in which the vehicle can move during a parking operation. An area and dimension of the moving area displayed on the display changes based on a change in a steering angle of the vehicle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 16/867,119,filed May 5, 2020, which is a continuation of U.S. patent applicationSer. No. 16/566,352, filed Sep. 10, 2019 and now U.S. Pat. No.10,683,035, which is a continuation-in-part of U.S. patent applicationSer. No. 15/779,263, filed May 25, 2018 and now U.S. Pat. No.10,450,004, which is a National Phase application of International Pat.Appl. No. PCT/JP2016/005064, filed Dec. 6, 2016, and claims the benefitof Japanese Pat. Appl. No. 2015-239092, filed Dec. 8, 2015. The entiredisclosure of each of the above-identified documents, including thespecification, drawings, and claims, is incorporated herein by referencein its entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a parking assistance device, a parkingassistance method, and a non-transitory computer readable medium storinga parking assistance program, for assisting a driving operation forparking a vehicle.

2. Description of the Related Art

Recently, a parking assistance device that assists a driving operationfor parking a vehicle has been developed and put in practical use (forexample, PLT 1). A parking assistance device, described in PLT 1,calculates a recommended backward movement start position from which anown vehicle can reach a target parking position while maintaining asteering angle, and displays, on a display unit, a backward movementstart frame in addition to an own vehicle figure representing a positionof the own vehicle and a parking target frame showing the target parkingposition, to thereby assist a driving operation for parking.

According to the parking assistance device described in Japanese PatentNo. 4900232 (hereinafter referred as PLT 1), an own vehicle figure, aparking target frame, and a backward movement start frame are displayedas parking guidance. Therefore, a driver can easily recognize a targetparking position and a recommended backward movement start position. Byperforming a driving operation according to the parking guidance, thedriver can move the own vehicle to the target parking position and parkthe own vehicle.

SUMMARY

An object of the present disclosure is to provide a parking assistancedevice, a parking assistance method, and a non-transitory computerreadable medium storing a parking assistance program that enable parkingto be completed by a driving operation according to parking guidance,and enable driving efficiency for parking to be improved.

A parking assistance device according to the present disclosure includesan imager that captures an image of a surrounding of a vehicle, and adisplay that displays a guidance image for guiding the vehicle from aparking start position to a target parking position and displays amoving area in which the vehicle can move during a parking operation. Anarea and dimension of the moving area displayed on the display changesbased on a change in a steering angle of the vehicle.

A parking assistance method according to the present disclosure includesreceiving a captured image of a surrounding of a vehicle. The parkingassistance method further includes displaying a guidance image forguiding the vehicle from a parking start position to a target parkingposition and a moving area in which the vehicle can move during aparking operation. The parking assistance method further includeschanging an area and dimension of the displayed moving area based on achange in a steering angle of the vehicle.

A non-transitory computer readable medium according to the presentdisclosure recording a parking assistance program for causing a computerof a parking assistance device to perform processes of receiving acaptured image of a surrounding of a vehicle; displaying a guidanceimage for guiding the vehicle from a parking start position to a targetparking position and a moving area in which the vehicle can move duringa parking operation; and changing an area and dimension of the displayedmoving area based on a change in a steering angle of the vehicle.

According to the present disclosure, a parking route is set inconsideration of presence or absence of an obstacle on the parkingroute. Therefore, a driver can complete parking by a driving operationaccording to the parking guidance. Accordingly, driving efficiency forparking is improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a configuration of a parking assistancedevice according to an exemplary embodiment.

FIG. 2 illustrates a disposition state of on-vehicle cameras.

FIG. 3 illustrates an example of a display screen of a display unit.

FIG. 4A illustrates a steering icon.

FIG. 4B illustrates a steering icon.

FIG. 5 is a flowchart illustrating an example of a parking assistanceprocess.

FIG. 6 is a flowchart illustrating an example of a parking route settingprocess.

FIG. 7 is a flowchart illustrating an example of a parking guidingprocess.

FIG. 8 is a flowchart illustrating an example of a steering operationassistance process.

FIG. 9A illustrates an example of a parking operation.

FIG. 9B illustrates an example of a parking operation.

FIG. 10 illustrates an imaging area.

FIG. 11 illustrates an example of a moving area.

FIG. 12 illustrates another example of a moving area.

FIG. 13 illustrates an exemplary display for guiding parking.

FIG. 14 illustrates another exemplary display for guiding parking.

FIG. 15 illustrates an example of an obstacle area.

FIG. 16 illustrates another example of an obstacle area.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Prior to the description of an exemplary embodiment of the presentdisclosure, a problem in a conventional device is briefly described. Ina driving assistance device described in PLT 1, parking guidance ismerely performed according to a parking route calculated at a parkingstart position, and presence or absence of an obstacle on the parkingroute is not considered. Therefore, when there is an obstacle on theparking route, a driving operation may not be performed according to theparking guidance. In that case, a parking route is reset when thedriving operation cannot be performed. Accordingly, the operatingefficiency for parking may be lowered. In the worst case, a parkingroute cannot be generated and the system may be interrupted.

Hereinafter, an exemplary embodiment of the present disclosure will bedescribed in detail with reference to the drawings.

FIG. 1 is a diagram illustrating a configuration of parking assistancedevice 1 according to the present exemplary embodiment. Parkingassistance device 1 assists a driving operation for parking own vehicleV (see FIG. 2) at a target parking position. As illustrated in FIG. 1,parking assistance device 1 includes controller 11, imager 12, displayunit 13, sound output unit 14, operating unit 15, steering angle sensor16, and the like.

Controller 11 includes central processing unit (CPU) 111 as anarithmetic/control device, and random-access memory (RAM) 112 andread-only memory (ROM) 113 as main memories. CPU 111 reads from ROM 113a program in accordance with a processing content, deploys the programin RAM 112, and controls respective blocks in cooperation with thedeployed program.

ROM 113 stores, besides a basic program called a basic input outputsystem (BIOS), a parking assistance program for assisting a drivingoperation for parking a vehicle. Specific functions of controller 11will be described below.

Imager 12 is at least one on-vehicle camera mounted on own vehicle V. Asillustrated in FIG. 2, imager 12 includes front camera 121, rear camera122, right-side camera 123, and left-side camera 124, for example. Eachof on-vehicle cameras 121 to 124 is a wide angle camera having a fieldangle of about 180°, for example. On-board cameras 121 to 124 aredisposed so as to image the whole circumference of own vehicle V.

For example, front camera 121 is provided on a front grille of ownvehicle V, and captures an image of a front area in an obliquelydownward direction toward the ground. Rear camera 122 is provided on aroof spoiler of own vehicle V and captures an image of a rear area in anobliquely downward direction toward the ground. Each of right-sidecamera 123 and left-side camera 124 is provided on a side mirror of ownvehicle V, and captures an image of a side area in an obliquely downwarddirection toward the ground.

Display unit 13 is a display of a navigation system disposed on aninstrument panel, for example. Display unit 13 displays an image forguiding own vehicle V to a target parking position. Sound output unit 14is a speaker, for example, and outputs sound at the time of guiding ownvehicle V to the target parking position.

Operating unit 15 includes a main switch for enabling a parkingassistance function, a parking position setting button for setting atarget parking position, a route determination button for determining aparking route, and a parking mode selection button for setting necessityof steering wheel actuation operation.

Steering angle sensor 16 detects a current steering angle of steeringwheel SW.

Controller 11 functions as image management unit 11A, parking guidancecreating unit 11B, expected moving locus creating unit 11C, displaycontroller 11D, moving area determining unit 11E, and stop positiondetermining unit 11F.

Image management unit 11A acquires an image captured by imager 12, andstores it temporarily. Further, image management unit 11A creates awhole circumferential view image by combining a plurality of imagescaptured by imager 12.

Parking guidance creating unit 11B creates parking guidance informationshowing an ideal parking route, based on basic information including acurrent position (parking start position) of own vehicle V, a set targetparking position, and a surrounding environment (presence or absence ofan obstacle). The parking guidance information includes a steeringposition, a parking guide line, a target steering angle, and the like.

The steering position means a position at which a turn is made at thetime of parking own vehicle V, including a backward movement startposition or a steering wheel actuation operation position. The targetsteering angle means a steering angle for guiding own vehicle V to amoving target position including the steering position or the targetparking position. This means that when the steering angle is set to thetarget steering angle, own vehicle V can be guided to the moving targetposition without any steering operation thereafter.

It should be noted that while parking guidance creating unit 11B createsparking guidance information when operating unit 15 performs anoperation to set the target parking position, definitive parkingguidance information is determined based on the steering angle whenparking is started. The parking guidance information may also be finelyadjusted when moving to the steering position is completed.

Expected moving locus creating unit 11C creates an expected moving locusbased on the current position and the current steering angle of ownvehicle V. The expected moving locus is a locus of the own vehicle whenit moves in a state of keeping the current steering angle.

Display controller 11D controls a display mode of an image on displayunit 13. Display controller 11D displays, on display unit 13, a guidanceimage for guiding own vehicle V to the target parking position, forexample.

FIG. 3 illustrates an example of a display screen of display unit 13. Asillustrated in FIG. 3, display unit 13 includes whole circumferentialview display area 131, front/rear view display area 132, icon displayarea 133, and message display area 134.

Whole circumferential view display area 131 displays a wholecircumferential view as if the vehicle is seen downward from the above.Such a view is created by combining images captured by imager 12. Inwhole circumferential view display area 131, stop icons indicating stoppositions including a target parking position and a steering positionare displayed in a superimposed manner on the captured images. Here, astop icon includes letters “stop” and an image of a stop line.

Front/rear view display area 132 displays an image captured by frontcamera 121 or rear camera 122. The display image in front/rear viewdisplay area 132 is switched based on a traveling direction (gearposition) of own vehicle V. In front/rear view display area 132, aparking guide line and an expected moving locus are displayed in asuperimposed manner on the captured image.

In icon display area 133, icons I1, I2 representing information relatedto parking assistance are displayed. Icon I1 is an icon for instructingan angle of a steering wheel (hereinafter referred to as a “targetsteering angle”) to be operated (hereinafter referred to as “steeringicon I1”). Icon I2 is an icon showing an area displayed in front/rearview display area 132 (front side in FIG. 3).

In message display area 134, information related to parking assistanceis displayed as a message. In message display area 134, a warningmessage for parking, a message instructing a driving operation thatshould be performed by a driver, a message informing completion ofmoving to a moving target position, and the like are displayed, forexample. These messages are displayed in message display area 134, andare also output as sound from sound output unit 14.

FIGS. 4A and 4B illustrate steering icon I1. FIG. 4A illustrates a casewhere current steering angle θ is 23 degrees, and target steering angleϕ is 100 degrees. FIG. 4B illustrates a case where current steeringangle θ is 90 degrees, and target steering angle ϕ is 100 degrees.

As illustrated in FIGS. 4A, 4B, steering icon I1 includes first icon I11showing current steering angle θ, second icon I12 showing a given anglerange around target steering angle ϕ, and third icon I13 showing currentsteering angle θ and target steering angle ϕ in numerical values.

In the present exemplary embodiment, steering angles θ, ϕ are indicatedas a positive angle in a clockwise direction and a negative angle in acounterclockwise direction, with a state of steering wheel SW instraight traveling being used as a reference (0°).

First icon I11 includes an image of a steering wheel and an index lineindicating steering angle θ, for example. Second icon I12 is an arcuateband image along an outer circumference of the steering wheel of firsticon I11, for example, and may include an index line indicating targetsteering angle ϕ.

First icon I11 and third icon I13 (numerical values representing currentsteering angle θ) vary as steering wheel SW is operated. Second icon I12is set based on the current position and the moving target position ofown vehicle V. With second icon I12, a driver can intuitively recognizehow much he/she should operate steering wheel SW.

Further, with third icon I13, as current steering angle θ and targetsteering angle ϕ are represented as numerical values, it is possible toprevent an operating direction of the steering wheel from beingrecognized erroneously. Even in a case where the target steering angle θis 360 degrees or larger, recognition can be made reliably.

The given angle range around target steering angle ϕ is ±20°, forexample. When steering angle θ is within a range of ±20°, the steeringangle of a tire can be considered to be almost the same. Accordingly,own vehicle V can be guided to the moving target position. It is onlynecessary that the given angle range is a range in which a steeringangle of a tire corresponding to steering angle θ can be deemed to besimilar. The given angle range may be set appropriately depending on avehicle on which parking assistance device 1 is mounted.

It is preferable that a display mode of second icon I12 be changedaccording to current steering angle θ. For example, a display color iscontrolled to be changed such that the color is “red” when currentsteering angle θ is largely deviated from target steering angle ϕ, thecolor is “yellow” when it comes close to target steering angle θ, andthe color is “green” when it enters the given angle range. Thereby, thedriver can easily recognize how much he/she should further operatesteering wheel SW.

In conjunction with a change in the display mode of second icon I12, adisplay mode of third icon I13 may be changed. The display mode to bechanged is not limited to the display color. The display mode can bechanged from lighting display to flicking display (or from flickingdisplay to lighting display), for example.

FIG. 5 is a flowchart illustrating an example of a driving assistanceprocess performed by controller 11. This process is realized when CPU111 calls out a parking assistance program stored in ROM 113 andexecutes it, along with an operation by a driver in operating unit 15,for example.

Here, specific description will be given on a parking operation of acase where after own vehicle V is moved from a parking start position toa backward movement start position as illustrated in FIG. 9A, ownvehicle V is moved to a target parking position and parked inperpendicular parking, as illustrated in FIG. 9B.

In step S1 of FIG. 5, controller 11 performs a parking route settingprocess. Specifically, the parking route setting process is performedaccording to the flowchart of FIG. 6.

That is, in step S101 of FIG. 6, controller 11 determines whether or notthe target parking position is set by the driver. As illustrated in FIG.9A, for example, the driver can set the target parking position byoperating the parking position setting button of operating unit 15, in astate where the own vehicle is stopped at a side of the target parkingposition (parking start position). When the target parking position isset by the driver (“YES” in step S101), a process of step S102 starts.

In step S102, controller 11 acquires an image captured by imager 12 (aprocess as image management unit 11A). Imager 12 images an imaging areaillustrated in FIG. 10, for example. Even after step S102, controller 11sequentially acquires images captured by imager 12.

In step S103, controller 11 acquires a current steering angle based on adetection result of steering angle sensor 16.

In step S104, controller 11 creates parking guidance information forguiding own vehicle V from the parking start position to the targetparking position (a process as parking guidance creating unit 11B).Specifically controller 11 creates a whole circumferential view imageand calculates an ideal parking route (hereinafter referred to as “afirst parking route”), based on basic information including a currentposition (parking start position) of own vehicle V, the set targetparking position, and a surrounding environment (presence or absence ofan obstacle), for example.

Controller 11 also calculates a parking route to be used for actualparking guidance (hereinafter referred to as a “second parking route”),based on the basic information and the current steering angle.

Here, whether or not steering wheel actuation operation is required isalso determined by controller 11. In the case of the parking operationillustrated in FIGS. 9A, 9B, a parking route in which a steeringposition (backward movement start position) is set as a moving targetposition, and a parking route in which the target parking position isset as a moving target position, are calculated.

In step S105, controller 11 specifies a moving area when own vehicle Vmoves according to the second parking route (a process as moving areadetermining unit 11E). The moving area is an area in which own vehicle Vcan move according to the second parking route, and is calculated inconsideration of a whole length and a vehicle width of own vehicle V.

In step S106, controller 11 displays moving area AR together with thecurrent position of own vehicle V, in whole circumferential view displayarea 131 (see FIGS. 11, 12). At that time, it is preferable to changethe display mode (display color, for example) of moving area AR,depending on a number of steering wheel actuation operation included inthe parking guidance information. Thereby, the driver can recognizeeasiness of the parking operation, based on the display mode of movingarea AR. It should be noted that while moving area AR is illustrated asa simple figure in FIGS. 11 and 12, it is actually a much morecomplicated figure. Further, while FIGS. 11, 12 illustrate moving areaAR, it is also possible to display a figure of obstacle area BR havingan obstacle, on the contrary, as illustrated in FIGS. 15, 16.

In message display area 134, a message prompting to confirm that thereis no obstacle such as a parked vehicle in moving area AR. This messageis also output from sound output unit 14. The driver confirms whetherthere is no obstacle in moving area AR. In a case where there is anobstacle in moving area AR, parking operation cannot be completed withthe second parking route calculated based on current steering angle θ.Therefore, the driver performs a steering operation to avoid theobstacle in moving area AR. In a case where obstacle area BR isdisplayed, the driver performs a steering operation such that there isno obstacle other than obstacle area BR.

At that time, in icon display area 133, it is possible to displaysteering icon I1 showing a steering angle for moving own vehicle V tothe backward movement start position on the first parking route.Alternatively a steering operation assistance process, described below,may be performed. A steering operation is performed promptly such thatcurrent steering angle θ becomes target steering angle ϕ shown bysteering icon I1, while presence or absence of an obstacle in movingarea AR is checked.

In step S107, controller 11 determines whether or not a steeringoperation is performed. When the steering operation is performed (“YES”in step S107), the process of step S103 starts. When the steeringoperation is not performed (“NO” in step S107), a process of step S108starts.

When the steering operation is performed, a second parking route iscalculated anew based on steering angle θ after the operation, andmoving area AR is updated. For example, when the steering operation isperformed toward a positive side from the state illustrated in FIG. 11and the steering angle is increased, moving area AR is updated such thatthe front side of own vehicle V is reduced and the right side thereof isexpanded, as illustrated in FIG. 12. In a case of displaying obstaclearea BR, the front side of own vehicle V is expanded and the right sidethereof is reduced.

In step S108, controller 11 determines whether or not the driverperforms an operation to determine a parking route (operation of aparking route determination button, for example). When the operation todetermine the parking route is performed (“YES” in step S108), a processof step S109 starts. When the operation to determine the parking routeis not performed (“NO” in step S108), the process of step S107 starts.The driver recognizes moving area AR that varies according to a steeringoperation, and confirms that there is no obstacle interrupting theparking operation on the second parking route. Then, the driver fixesthe parking route. In a case of displaying obstacle area BR, the driverrecognizes obstacle area BR that varies according to a steeringoperation, and confirms that there is no obstacle interrupting theparking operation in an area other than obstacle area BR on the secondparking route. Then, the driver fixes the parking route.

In step S109, controller 11 sets the second parking route when thedetermination operation is performed by the driver, to be a parkingroute for which parking guidance is provided. Parking guidance isprovided according to the set second parking route. When the parkingroute setting process ends, a process of step S2 of FIG. 5 starts.

In this way, a definitive parking route is set after confirming thatthere is no obstacle interrupting the parking operation on the parkingroute when a steering operation for moving to the backward movementstart position is performed. Accordingly, the parking operationaccording to the parking guidance is never interrupted by an obstacle.

In step S2 of FIG. 5, controller 11 performs a parking guiding process.Specifically, the parking guiding process is performed according to theflowchart of FIG. 7. Own vehicle V is guided up to the backward movementstart position by the parking guiding process from the parking startposition, and is guided up to the target parking position by the parkingguiding process from the backward movement start position.

That is, in step S201 of FIG. 7, controller 11 specifies a parkingposition based on the set parking route (a process as stop positiondetermining unit 11F). The stop position is equivalent to the movingtarget position, and includes the backward movement start position, thesteering wheel actuation operation position, or the target parkingposition. In the parking guiding process, display/non-display of a stopicon at the specified stop position is controlled according to anapproaching state of own vehicle V relative to the stop position.

In step S202, controller 11 displays first parking guidance without anystop icon. That is, after the parking operation is started from theparking start position toward the backward movement start position (stopposition), or after the parking operation is started from the backwardmovement start position toward the target parking position, the stopicon is not displayed for a given period (see FIG. 13).

In message display area 134, a message prompting a forward movement withthe steering wheel being fixed is displayed. This message is also outputfrom sound output unit 14. According to this instruction, a forwardmoving operation or a backward moving operation is started promptly.When the forward movement or the backward movement is started, ownvehicle V smoothly moves toward the moving target position. Displays inwhole circumferential view display area 131 and front/rear view displayrea 132 are changed as own vehicle V moves.

In step S203, controller 11 determines whether or not own vehicle V hasapproached the stop position. For example, when an approaching distanceof own vehicle V to the stop position is about 1.0 m, it is determinedthat own vehicle V has approached the stop position. When own vehicle Vhas approached the stop position (“YES” in step S203), a process of stepS204 starts. When own vehicle V has not approached the stop position(“NO” in step S203), the process moves to step S202.

In step S204, controller 11 displays second parking guidance with a stopicon. This means that when own vehicle V approaches the backwardmovement start position (stop position) to some extent, stop icon I3appears for the first time (see FIG. 14).

After stop icon I3 is displayed, a display color or transparency may bechanged such that the visibility thereof is gradually improved accordingto an approaching state of own vehicle V toward the stop position.Specifically, it is possible to change the icon from a less visible mode(pale color display, high transparency) to an easily visible mode (deepcolor, low transparency) as the approaching distance becomes closer. Itis also possible to inform the approaching state of the own vehicletoward the stop position by an informing unit other than display unit13. As the informing unit, sound output unit 14 is applicable, forexample. Further, a vibrator (not illustrated) that vibrates a seat orthe steering wheel is also applicable.

In message display area 134, a message prompting to stop at the positionof stop icon I3 is displayed. This message is also output from soundoutput unit 14. Thereby, the driver watches the stop position in theparking guidance, and stops traveling at a point when own vehicle Vreaches the parking position.

As described above, stop icon I3 is not displayed from the beginning ofthe parking operation, but is displayed only when own vehicle Vapproaches the stop position. Thereby, the driver does not watch onlythe parking guidance in an attempt to make the own vehicle follow thestop icon from the beginning of the parking operation. Accordingly, thedriver can sufficiently watch surrounding obstacles not displayed,whereby the safety is improved.

In step S205, controller 11 determines whether or not own vehicle V hasreached the stop position. As illustrated in FIGS. 9A and 9B, when ownvehicle V moves forward from the parking start position to the backwardmovement start position, the backward movement start position is thestop position. Meanwhile, when own vehicle V moves backward from thebackward movement start position to the target parking position, thetarget parking position is the stop position. Whether or not own vehicleV has reached the stop position can be determined based on an imagingresult by imager 12, for example. When own vehicle V has reached thestop position (“YES” in step S205), a process of step S206 starts. Whenown vehicle V has not reached the stop position (“NO” in step S205), theprocess moves to step S204.

In step S206, controller 11 displays a message prompting a stop inmessage display area 134, and also outputs it from sound output unit 14.Thereby, the driver performs a stop operation, and own vehicle V stopsat the stop position. When the parking guiding process ends, a processof step S3 in FIG. 5 starts.

In step S3 of FIG. 5, controller 11 determines whether or not ownvehicle V has reached the target parking position. Whether or not ownvehicle V has reached the target parking position can be determinedbased on an imaging result by imager 12, for example. When own vehicle Vfinally has reached the target parking position (“YES” in step S3), afact that the vehicle has reached the target parking position isinformed, and the parking assistance process ends. At that time, it mayinstruct to return the steering wheel to a reference state and movestraight backward to complete the parking operation.

On the other hand, when own vehicle V has not reached the target parkingposition (“NO” in step S3), that is, when own vehicle V is in a state ofreaching the steering position (backward movement start position orsteering wheel actuation operation position), the process of step S4starts, and a steering operation assistance process is performed. Inthat case, a fact that own vehicle V has reached the steering positionis informed, and an instruction is given to switch the gear from forwardmovement to backward movement, or from backward movement to forwardmovement. Specifically, the steering operation assistance process isperformed according to the flowchart of FIG. 8.

In S401 of FIG. 8, controller 11 switches an image in front/rear viewdisplay area 132 along with a gear change operation by the driver, andupdates an icon image in icon display area 133.

At that time, in message display area 134, a message instructing asteering operation for allowing steering angle θ to fall within a rangeshown by second icon I12 is displayed. With steering icon I1, the drivercan easily recognize how much he/she should operate steering wheel SW.Thereby, the instructed steering operation is performed promptly.

In step S402, controller 11 determines whether or not the steeringoperation is performed by the driver. When the steering operation isperformed by the driver (“YES” in step S402), a process of step S403starts.

In step S403, controller 11 updates steering icon I1 along with thesteering operation by the driver. Specifically, along with the steeringoperation by the driver, first icon I11 (an image of the steering wheeland an index line of steering angle θ) is turned, and a numerical valuerepresenting current steering angle θ of third icon I13 is changed.

In step S404, controller 11 determines whether or not steering angle θfalls within a given angle range. When steering angle θ falls within thegiven angle range (“YES” in step S404), a process of step S405 starts.When steering angle θ does not fall within the given angle range (“NO”in step S404), the process of step S402 starts.

In step S405, controller 11 changes the display mode (display color, forexample) of second icon I12 and third icon I13. Thereby, the driver caneasily recognize that current steering angle θ is in an appropriatestate.

In step S406, controller 11 displays, in message display area 134, amessage informing that steering angle θ is in the appropriate state andinforming a start of parking guidance. When the steering operationassistance process ends, the process of step S2 of FIG. 5 starts. By theparking guiding process after the steering operation assistance process,own vehicle V is finally guided to the target parking position.

As described above, as target steering angle ϕ is displayed with an iconshowing a range of a required operation amount of the steering wheel,the driver can intuitively recognize how much he/she should operate thesteering wheel. Accordingly the driver can complete the requiredsteering operation in a short time without being excessively consciousof target steering angle ϕ. Thereby, the driving efficiency for parkingis improved.

As described above, parking assistance device 1 according to the presentexemplary embodiment includes imager 12 that captures an image of asurrounding of own vehicle V, display unit 13 that displays a guidanceimage for guiding own vehicle V from a parking start position to atarget parking position, parking guidance creating unit 11B that createsparking guidance information showing a parking route, based on basicinformation including an imaging result by imager 12, the parking startposition, and the target parking position, moving area determining unit11E that determines moving area AR in which own vehicle V can move,based on the parking guidance information, and display controller 11Dthat displays, on display unit 13, an image showing moving area ARtogether with the guidance image based on guidance information.

According to parking assistance device 1, a parking route is set inconsideration of presence or absence of an obstacle on the parkingroute. Therefore, a driver can complete parking by a driving operationaccording to the parking guidance. Accordingly, driving efficiency forparking is improved.

Although the disclosure made by the present inventor has beenspecifically described above based on the exemplary embodiment, thepresent disclosure is not limited to the above exemplary embodiment, andcan be modified without departing from the gist of the presentdisclosure.

For example, it is possible to allow a driver to select a parking modeinvolving steering wheel actuation operation or a parking mode notinvolving steering wheel actuation operation. In that case, parkingassistance device 1 calculates an ideal parking route according to theselected parking mode. It is also possible that after a target parkingposition is set at a parking start position, the own vehicle moveswithout parking guidance up to a backward movement start position, andthen parking guidance starts from the backward movement start position.

The present disclosure is applicable not only to a case of performingperpendicular parking but also to a case of performing parallel parkingin which a large number of steering wheel actuation operation isexpected.

Furthermore, moving area AR may be displayed by lines that indicate theoutside edges or periphery of moving area AR. For example, moving areaAR may be displayed by frame-shaped straight lines that surround movingarea AR. Alternatively, moving area AR may be displayed by a pair ofstraight lines that sandwich moving area AR along a width direction ofown vehicle V or along a traveling direction of own vehicle V.Furthermore, the lines that indicate the outside edges or periphery ofmoving area AR are not limited to straight lines, and may be curvedlines. In the case where moving area AR is displayed by the lines, innerarea of moving area AR may be displayed with a color different from thatof the outside edges or periphery of moving area AR. Such a color-codingallows moving area AR to be emphatically displayed.

Meanwhile, controller 11 may communicate with an external terminal anddisplay moving area AR together with the current position of own vehicleV on a display of the external terminal. Such configuration can be usedwhen a user performs parking assistance by operating the externalterminal from outside of own vehicle V, for example, such as “remoteparking”. According to the configuration, the user can check moving areaAR even when the user exists outside of own vehicle V. Therefore, theuser can confirm whether or not there is no obstacle in moving area ARand moving area AR is safe for own vehicle V.

Moreover, moving area AR may include the second parking route and apossibly moving area. The second parking route is defined as a route ofown vehicle from the parking start position to the target parkingposition and an area having a predetermined width along the route. Thewidth is, for example, the vehicle width of own vehicle or slightlylarge of the vehicle width of own vehicle. The possibly moving area isdefined as an area in which own vehicle may probably travel off of thesecond parking route. Own vehicle travels within the second parkingroute; however, does not necessarily travel within the possibly movingarea. According to the configuration, the user can confirm whether ornot there is no obstacle in the possibly moving area and the possiblymoving area is safe for own vehicle V when own vehicle V becomes off ofthe second parking route. Examples of the case of traveling off of thesecond parking route include a case where it occurs due to a time lagbetween the braking timing requested to the user by the parkingassistance device and the actual braking operation timing by the user.Note that moving area determining unit 11E only has to specify, asmoving area AR, an area including the area defined as the second parkingroute and a predetermined area. The predetermined area may be determinedin consideration of the whole length, the vehicle width, and the like ofown vehicle V.

Furthermore, the guidance image only has to an image for guiding ownvehicle V from the parking start position to the target parkingposition. For example, the guidance image may be a whole circumferentialview image, a front view image, or a rear view image. Alternatively, theguidance image may be a combination image of two or more of a wholecircumferential view image, a front view image, and a rear view image.Further alternatively, the guidance image may be a synthetic image inwhich stop icons, a moving area, a parking target frame, and a backwardmovement start frame are overlapped on one of a whole circumferentialview image, a front view image, and a rear view image.

In the present exemplary embodiment, the parking assistance processdescribed above is realized through execution of a parking assistanceprogram by controller 11. However, it can be realized by using ahardware circuit. The parking assistance program can be provided tocontroller 11 by being stored on a computer-readable storage medium suchas a magnetic disk, an optical disk, a flash memory, or the like. Theparking assistance program can also be provided by being downloaded viaa communication line such as the Internet.

It should be construed that the exemplary embodiment disclosed herein isillustrative in all aspects, and is not restrictive. The scope of thepresent disclosure is represented by the scope of the claims and not bythe above description, and it is intended that all modifications withinthe sense and scope equivalent to the claims are involved in the scopeof the present disclosure.

The parking assistance device, the parking assistance method, and theparking assistance program according to the present disclosure arepreferable in a case of parking a vehicle at a target parking position.

What is claimed is:
 1. A control method of a driving assistance deviceconfigured to be mounted in a vehicle comprising: receiving a firstambient image of the vehicle, the first ambient image captured by aplurality of cameras mounted in the vehicle; displaying a first overheadimage of the vehicle on a screen of a display mounted in the vehicle, atleast a part of the first overhead image corresponding to the firstambient image, the first overhead image including a vehicle imageindicating the vehicle, a first line segment overlapping the firstoverhead image on the screen, a second line segment overlapping thefirst overhead image on the screen, the first line segment having afirst end point and a second end point, the first line segment arrangedalong a traveling direction of the vehicle on the screen, the first endpoint being farther from the vehicle image than the second end point onthe screen, the second line segment having a third end point and afourth end point, the second line segment arranged along the travelingdirection of the vehicle on the screen, the third end point beingfarther from the vehicle than the fourth end point on the screen, andthe first line segment and the second line segment having a firstdistance between the first end point and the third end point on thescreen, when a steering angle of the vehicle equals to a first anglefrom a reference angle; receiving a second ambient image of the vehicle,the second ambient image captured by the plurality of cameras mounted inthe vehicle; displaying a second overhead image of the vehicle on thescreen, at least a part of the second overhead image corresponding tothe second ambient image, the second overhead image including thevehicle image, a third line segment overlapping the second overheadimage on the screen, a fourth line segment overlapping the secondoverhead image on the screen, the third line segment having a fifth endpoint and a sixth end point, the third line segment arranged along thetraveling direction of the vehicle on the screen, the fifth end pointbeing farther from the vehicle image than the sixth end point on thescreen, the fourth line segment having a seventh end point and a eighthend point, the fourth line segment arranged along the travelingdirection of the vehicle on the screen, the seventh end point beingfarther from the vehicle than the eighth end point, and the third linesegment and the fourth line segment having a second distance between thefifth end point and the seventh end point on the screen, when thesteering angle of the vehicle equals to a second angle from thereference angle; and the second length being greater than the firstlength, when the steering angle of the vehicle equals to the secondangle from the reference angle.
 2. The control method of the drivingassistance device according to claim 1, wherein the reference anglecorresponds to a neutral state of the steering wheel directing thevehicle to travel in a straight line.
 3. The control method of thedriving assistance device according to claim 1, wherein displaying, onthe screen, the first overhead image with a first steering angleindicator indicating the first angle, and displaying, on the screen, thesecond overhead image with a second steering angle indicator indicatingthe second angle.
 4. The control method of the driving assistance deviceaccording to claim 1, wherein displaying the first overhead image of thevehicle on the screen, when the steering angle of the vehicle equals tothe first angle, while the vehicle is traveling from a parking startposition to a target parking position, and displaying the secondoverhead image of the vehicle on the screen, when the steering angle ofthe vehicle equals to the second angle, while the vehicle is travelingfrom the parking start position to the target parking position.
 5. Thecontrol method of the driving assistance device according to claim 1,further comprising: receiving a third ambient image of the vehicle, thethird ambient image captured by the plurality of cameras mounted in thevehicle; displaying a third overhead image of the vehicle on the screen,at least a part of the third overhead image corresponding to the thirdambient image, the third overhead image including the vehicle image, afifth line segment overlapping the third overhead image on the screen, asixth line segment overlapping the third overhead image on the screen,the fifth line segment having a ninth end point and a tenth end point,the fifth line segment arranged along the traveling direction of thevehicle on the screen, the ninth end point being farther from thevehicle than the tenth end point, the sixth line segment having aeleventh end point and a twelfth end point, the sixth line segmentarranged along the traveling direction of the vehicle on the screen, theeleventh end point being farther from the vehicle than the twelfth endpoint, and the fifth line segment and the sixth line segment having athird distance between the ninth end point and the eleventh end pointwhen the steering angle of the vehicle equals to a third angle from thereference angle; and changing the third distance based on a change inthe steering angle of the vehicle.
 6. The control method of the drivingassistance device according to claim 5, wherein when the differencebetween the steering angle of the vehicle and the reference angleincreases in the clockwise direction, the third length becomes longerrightward facing one longitudinal direction of the vehicle image, on thescreen.
 7. The control method of the driving assistance device accordingto claim 1, wherein each of the first overhead image and the secondoverhead image is displayed on a first part of the screen of thedisplay, and a front view or a rear view from one of the plurality ofcameras is displayed on a second part of the screen of the display, thesecond part of the display being distinct from the first part of thedisplay.
 8. The control method of the driving assistance deviceaccording to claim 1, wherein displaying the seventh line segmentbetween the first end point and the third end point.